Dorsalspines
(total): 0;
Dorsalsoft rays
(total): 0;
Analspines: 0;
Analsoft rays: 0. A large thresher with relatively small eyes, curved, narrow-tipped pectoral fins, a narrow-tipped caudal fin, and a conspicuous white patch over the pectoral fin bases (Ref. 5578). Second dorsal origin well behind the rear tip of the pelvic fin (Ref. 559). Upper lobe of caudal fin very long and strap-like, about as long as or longer than length of rest of shark; lower lobe short but well developed (Ref. 13570). Brown, grey, blue-grey, or blackish on back and underside of snout, lighter on sides and abruptly white below; a white area extends from the abdomen over the pectoral-fin bases; pectoral-, pelvic-, and dorsal fins blackish, white dots sometimes present on pectoral-, pelvic-, and caudal- fin tips (Ref. 13570).

Cosmopolitan in temperate and tropical seas (Ref. 6871, 58085). Population considered reduced (R) in the US Atlantic waters; lower risk/conservation dependent (LR/CD) in US Pacific waters; data deficient (DD) in the rest of Atlantic and rest of Pacific (Ref. 12451). Highly migratory species, Annex I of the 1982 Convention on the Law of the Sea (Ref. 26139).

Biology
Glossary
(e.g. epibenthic)

Coastal over continental and insular shelves and epipelagic far from land (Ref. 30573, 43278, 58302). Oceanic although most abundant near land, pelagic at 1-366 m (Ref. 58302). Young often close inshore and in shallow bays (Ref. 5578). Feeds on schooling fishes (including mackerels, bluefishes, clupeids, needlefishes, lancetfishes and lanternfishes), squid, octopi, pelagic crustaceans, and rarely seabirds (Ref. 247). Ovoviviparous, embryos feeding on yolk sac and other ova produced by the mother (Ref. 43278, 50449). Uses its long caudal fin to bunch up and stun prey (Ref. 2850). Spatial and depth segregation by sex in northwestern Indian Ocean populations (Ref. 247). A few attacks on boats are doubtfully attributed to this species, but it is otherwise apparently harmless to humans, though the size of adults of this species command respect (Ref. 247). May cause damage to fishing gear (Ref. 6885). Valued for its meat, liver, hide, and fins; utilized fresh, dried-salted, smoked, and frozen (Ref. 9987).